Alkali food processing

Chapters 1 through 6 outline our understanding of the enzymes necessary or potentially useful for biomass conversion. Included are chapters on fuels and chemical feedstock production, pulp and paper processing, waste processing and degradation, food processing, and specific classes of alkali or thermostable enzymes. 

Electrodialysis is by far the largest use of ion exchange membranes, principally to desalt brackish water or (in Japan) to produce concentrated brine. These two processes are both well established, and major technical innovations that will change the competitive position of the industry do not appear likely. Some new applications of electrodialysis exist in the treatment of industrial process streams, food processing and wastewater treatment systems but the total market is small. Long-term major applications for ion exchange membranes may be in the nonseparation areas such as fuel cells, electrochemical reactions and production of acids and alkalis with bipolar membranes. 

Once dehydrated, the microfibrils are practically without functionality in ordinary food processing and preparation operations, because the inert microcrystallites are difficult for water to penetrate. The polymorphs, cellulose I and II (Blackwell, 1982 Coffey el al., 1995), are differentiated by their molecular orientation, hydrogen-bonding patterns, and unit-cell structure. Cellulose I is the natural orientation cellulose II results from NaOH treatment under tension of cellulose I with 18-45% alkali (mercerization). The I—II transition is irreversible. Mercerization strengthens the fibers and improves their lustre and affinity for dyes (Sisson, 1943). Sewing thread was relatively pure mercerized cotton until the advent of synthetic polymer fibers. 

The reactions of proteins in alkaline solution are very important from a number of standpoints. We have already discussed several uses of alkali treatment in food processing in the introduction. When contact between the food and alkali is kept to a minimum at the lowest temperature possible with adequate control of mixing, etc. there is presently no apparent reason to discontinue its use. Low levels of lysinoalanine occur in food which has been processed in the absence of added alkali, even at pH 6 and in the dry state (20). For example, the egg white of an egg boiled three minutes contained 140 ppm of lysinoalanine while dried egg white powder contained from 160 to 1820 ppm of lysinoalanine depending on the manufacturer (20). No lysinoalanine was found in fresh egg white, 3 Elimination and addition of lysine to the double bond of dehydroalanine reduce the level of the essential amino acid lysine. This can be prevented by adding other nucleophiles such as cysteine to the reaction. Whether lysinoalanine (and other compounds formed by addition reactions) is toxic at low levels in humans is not known. 

The effect of the cost of the ion exchange membrane on the total cost of electrodialysis or electrolysis is large because the membrane is relatively expensive. The lifetime of the membrane depends on the purpose and conditions of electrodialysis or electrolysis. A membrane for the electrodialytic concentration of seawater to produce sodium chloride has a lifetime of over 10 years, and that in the chlor-alkali membrane process, which is operated at ten times or more higher current density than that of seawater concentration, is over 5 years. However, in applications for food industries, the lifetime of the membrane is relatively short due to periodical sanitary cleaning of the electrodialyzer by acid or alkali solution, and sometimes oxidizing agents. 

Amino acids in animal and plant proteins appear to occur solely as L-isomers. However, D-amino acids are observed widely in nature as constituents of bacterial cell walls and of several antibiotics ( ) In addition, the heat and alkali treatments used in food processing can produce racemization of amino acids (4-6). 

While several laboratories have shown that severe racemiza-tion of proteins can occur during treatment with sodium hydroxide (6,18,22-24,61,62) the effects of other alkalis used in food processing are documented less well. Jenkins, et al. (70) have observed substantial differences in the degree of racemization caused by lime or caustic soda treatment of zein. Lime causes only 50% to 90% of the racemization observed for several amino acyl residues compared to when caustic soda is used. Because a substantial amount of calcium ion remained bound to the protein (approx. 10,000 ppm) compared to l/20th that amount of sodium ion for the caustic soda-treated zein, it is possible that divalent calcium may stabilize the protein making it less susceptible to racemization. Tovar (14) observed increases of 40% to 50% in serine and phenylalanine racemization and a decrease of 30% aspartate racemization for caustic soda-treated fish protein concentrate compared to lime-treated protein (see Table II). These studies indicate that different alkalis have different effects on racemization of proteins specifically, lime may cause less racemization than caustic soda at a similar pH. 

There are numerous sources of chitin (Fig. 1) and chitosan is obtained by deacetylatmg chitin with a hot alkali solution. Chitin has been found in a wide array of natural sources, namely crustaceans, fungi, yeasts, insects, annelids, nematodes, mollusks, coelenterate, marine diatoms, squid pens, etc. [16-19]. However, chitosan is primarily manufactured from the exoskeleton of crustaceans (crab, shrimp, prawn, lobster, krill, and crayfish) because of its abundant availability as a by-product of food processing [20, 21]. 

Although a number of cellulose ethers are known, the ethyl derivative is the only member finding plastics uses, mainly as a surface coating others are water-soluble and are used in food processing. Commercial ethyl cellulose contains 2.15 to 2.6 ethyl groups per repeat unit and is obtained by treatment of alkali cellulose with ethyl chloride. It finds use in compositions for the strippable protection of metal parts. 

The major chemical reactions that take place during food processing, as would be expected, occur between the main food components—the carbohydrates, proteins, fats and vitamins. These components can react with each other and with various food additives such as nitrites, sulphite, aldehydes and alkali to give food products of lower nutritional value to produce desirable and undesirable browning and flavours and very occasionally to produce toxic materials. 

Uses AnSfoam for textiles, laundry detergents, etiluent treatment and waste water, leather industry, agrochemicals, food processing applies., bottle washing Features Outstanding efficiency, versatility economical available in emulsion fomn alkali resistant Properties Otf-wh. emulsion sp.gr. 1.0 Use Level 100-500 ppm... 

The oldest way to produce caramel is by heating sucrose in an open pan, a process named caramelization. Food applications require improvement in caramel properties such as tinctorial power, stability, and compatibility with food. Caramels are produced in industry by controlled heating of a rich carbohydrate source in the presence of certain reactants. Carbohydrate sources must be rich in glucose because caramelization occurs only through the monosaccharide. Several carbohydrate sources can be used glucose, sucrose, com, wheat, and tapioca hydrolysates. The carbohydrate is added to a reaction vessel at 50°C and then heated to temperatures higher than 100°C. Different reactants such as acids, alkalis, salts, ammonium salts, and sulfites can be added, depending on the type of caramel to be obtained (Table 5.2.2). 

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